Silica Fused

It should be noted that low levels of birefringenee ean be induced by mechanical stresses in materials that are not birefringent in their perfect crystalline state/ Such stresses are typically created if there are large thermal inhomogeneities in the furnaces in which the crystal of fused silica are grown/  

Fused silica is by far the primary optical material for lens manufacturing. Its mechanical and thermal properties are well known, and its grinding and polishing infrastructure are well established. It is relatively inexpensive and has good index homogeneity over large areas. Lens-grade fused silica, however, is an expensive material. The temperature-dependent properties of fused silica are summarized in Table 13.7. 

Birefringence in fused silica and Cap2 for lithography, Solid State TechnoL, 11 82 (Feb. 2000). 

Levinson, Principles of Lithography, 2nd ed., p. 163, SPIE Press, Bellingham, WA (2005). For a comparison of refractive index data of fused sihca from different suppliers, see for example, J. Mahtson, Interspecimen comparison of the refractive index of fused sihca, J. Opt. Soc. Amer. 35, 1205 (1965). 

Sakaguchi, S. Todoroki, and S. Shibata, Rayleigh scattering in sihca glasses, J. Amer. Ceramic Soc. 79, 2821 (1996). 

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Fig. VI-3. Attraction between fused-silica flat plates and spheres of radius 413.5 cm (I) or 83.75 cm (II). The lines are drawn with a slope of -3.00. (From Ref. 27.)...

When silica is fused,. silica glass is formed. This has advantages over ordinary glass in that it is much less easily fused (it softens at about 1800 K). and has a very low coefficient of expansion. It is. therefore, used for crucibles and other articles required to be infusible... 

Solid-phase microextractions also have been developed. In one approach, a fused silica fiber is placed inside a syringe needle. The fiber, which is coated with a thin organic film, such as poly(dimethyl siloxane), is lowered into the sample by depressing a plunger and exposed to the sample for a predetermined time. The fiber is then withdrawn into the needle and transferred to a gas chromatograph for analysis. 

Caffeine is extracted from beverages by a solid-phase microextraction using an uncoated fused silica fiber. The fiber is suspended in the sample for 5 min and the sample stirred to assist the mass transfer of analyte to the fiber. Immediately after removing the fiber from the sample it is transferred to the gas chromatograph s injection port where the analyte is thermally desorbed. Quantitation is accomplished by using a C3 caffeine solution as an internal standard. 

Capillary Columns Capillary, or open tubular columns are constructed from fused silica coated with a protective polymer. Columns may be up to 100 m in length with an internal diameter of approximately 150-300 )J,m (Figure 12.17). Larger bore columns of 530 )J,m, called megabore columns, also are available. 

Fused-silica fiber coated with stationary phase... 

A solid-phase extraction in which the solid adsorbent is coated on a fused-silica fiber held within a syringe needle. 

Microcolumns use less solvent and, because the sample is diluted to a lesser extent, produce larger signals at the detector. These columns are made from fused silica capillaries with internal diameters of 44—200 pm and lengths of up to several meters. Microcolumns packed with 3-5-pm particles have been prepared with column efficiencies of up to 250,000 theoretical plates. 

Capillary Tubes Figure 12.42 shows a cross section of a typical capillary tube. Most capillary tubes are made from fused silica coated with a 20-35-)J,m layer of poly-imide to give it mechanical strength. The inner diameter is typically 25-75 )J,m, which is smaller than that for a capillary GC column, with an outer diameter of 200-375 )J,m. 

A dynamic-FAB probe having a simple copper target. The narrow fused-silica tube passes through the shaft, its end lying flush with the target surface. 

Transparent fused silica can be formed at a temperature of 1200°C and a pressure of 13.8 MPa (2000 psi) from silica powder consisting of 15 nm ultimate particles (92) or by electric arc fusion of pure silica sand having low iron and alkali metal contents. The cooled product is ground to the desired particle size. Fused sihca is primarily manufactured by C-E Minerals, Minco, and Precision Electro Minerals in the United States by Chuo Denko, Denki Kagaku Kogyo, NKK, Showa Denko, and Toshiba Ceramics in Japan. Based on 1988 data and projected growth, an estimated 135,000 metric tons of fused siUca were used in 1994 as a sacrificial component or investment casting in the manufacture of metals and as a component in refractory materials (62). 

Table 8. Dielectric Properties of Synthetic Fused Silica ...

Fused Silica Code 7940 Data Sheet, Corning Glass Works, Coming, N.Y., 1992. 

Optical Fused Quarter and Fused Silica, Heraeus-Amersil, Inc., SayreviUe, N.J., 1981. 

We have developed the method for quantitative analysis of urinary albumin with CE. A capillary electrophoresis systems Nanophor 01 (Institute of Analytical Instmmentation, Russian Academy of Sciences, Saint-Petersburg) equipped with a UV-detector was used to determine analyte. Separation was achieved using 45 cmx30 p.m I.D. fused silica capillary column with UV-detection at 214 nm. 

It should be noted that not all materials satisfy these stability criteria. For example, over a range of low pressures, the sound speed of fused silica decreases with pressure, so shock waves cannot be supported. As pointed... 

L.M. Barker and R.E. Hollenbach, Shock-Wave Studies of PMMA, Fused Silica, and Sapphire, J. Appl. Phys. 41, 4208 (1970). 

Here, the wavelength of the laser light is A, and is a correction term due to the wavelength dependence of the refractive index of the etalon material ( = 0.034 at 514.5 nm when fused silica etalons are used to achieve the necessary delay, or = 0 when a lens combination is used). The optical correction term Av/v results from the change in refractive index of the window material with shock stress (Barker and Hollenbach, 1970). If the measure-... 

Typically specimens for reflectivity measurements are prepared on flat, smooth, rigid substrates. For example, these substrates can be polished fused silica, quartz, or silicon. It is important, however, that the substrates be thick to avoid distonions of the specimen when mounted in the reflectometer. Any curvature or bowing will increase the divergence of the incident beam and result in a deterioration of the resolution. 

Figure 1.2 Chromatogram of coal-tar oil obtained by using the following conditions column, Waters Spherisorb PAH 5 mm in 250 p.m id X 30 cm fused silica column oven temperature, 100°C UV detector wavelength to 254 nm mobile phase, 100 to 300 bar CO2 and 0.10 to 1.00 p.L min methanol over 30 minutes.

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